The invention relates to an apparatus and a method for checking value documents, in particular banknotes, and to a value document processing system.
In certain cases, banknotes are subsequently supplied with a marking ink. Thus, for example, certain regions of banknotes which are to be withdrawn from cash circulation are marked with a marking ink, in particular blackened, by national financial institutes. Further, marking ink is also used for theft protection, by the marking ink being released in the event of an unauthorized opening of a transport container for banknotes which is supplied with a so-called ink bomb system, so that the banknotes are wetted with the ink.
DE 10 2009 057 348 A1 discloses an apparatus for automatically recognizing banknotes marked with marking ink, wherein at least one of the surfaces of the banknote to be checked is detected with at least one sensor, and the presence of marking ink is checked on the basis of the data obtained from an edge region of the surface of the banknote.
In the known methods for checking banknotes it can occur that regions of a banknote supplied with marking ink cannot be distinguished with sufficient reliability from regions which are bent over or have dog-ears, so that these banknotes are incorrectly classified as being marked with a marking ink and are thus unintentionally removed from cash circulation, although these could have been returned into circulation.